IEX won approval, however. John Ramsay, chief market policy at the new exchange, said in an op-ed January 24 that "we have been operating as an exchange for over four months, and chaos has yet to descend on the world."

RELATED: Take a look at the state of the New York Stock Exchange before Trump's election:

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New York Stock Exchange before the election

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New York Stock Exchange before the election

Traders work on the floor of the New York Stock Exchange (NYSE) in New York City, U.S., November 7, 2016. REUTERS/Brendan McDermid

Traders work on the floor of the New York Stock Exchange (NYSE) in New York City, U.S., November 7, 2016. REUTERS/Brendan McDermid

Traders work on the floor of the New York Stock Exchange (NYSE) in New York City, U.S., November 7, 2016. REUTERS/Brendan McDermid

Traders work on the floor of the New York Stock Exchange (NYSE) in New York City, U.S., November 7, 2016. REUTERS/Brendan McDermid

Traders work on the floor of the New York Stock Exchange (NYSE) in New York City, U.S., November 3, 2016. REUTERS/Brendan McDermid

Pedestrians walk along Wall Street near the New York Stock Exchange (NYSE) in New York, U.S., on Monday, Oct. 31, 2016. U.S. stocks rose from a six-week low amid an increase in deal activity as traders assessed the outlook for the presidential election and interest rates in the world's largest economy. Photographer: Michael Nagle/Bloomberg via Getty Images

NEW YORK, NY - NOVEMBER 01: Traders work on the floor of the New York Stock Exchange (NYSE) on November 1, 2016 in New York City. As Wall Street continues to feel election uncertainty, the Dow Jones closes fell more than 100 points. (Photo by Spencer Platt/Getty Images)

A trader works on the floor of the New York Stock Exchange (NYSE) in New York, U.S., on Friday, Nov. 4, 2016. U.S. stocks fluctuated amid payrolls data that bolstered speculation the economy is strong enough to weather higher interest rates, while investors remained wary before the looming presidential election. Photographer: Michael Nagle/Bloomberg via Getty Images

Traders work on the floor of the New York Stock Exchange (NYSE) in New York, U.S., on Friday, Nov. 4, 2016. U.S. stocks fluctuated amid payrolls data that bolstered speculation the economy is strong enough to weather higher interest rates, while investors remained wary before the looming presidential election. Photographer: Michael Nagle/Bloomberg via Getty Images

NEW YORK, NY - NOVEMBER 01: Traders work on the floor of the New York Stock Exchange (NYSE) on November 1, 2016 in New York City. As Wall Street continues to feel election uncertainty, the Dow Jones closes fell more than 100 points. (Photo by Spencer Platt/Getty Images)

A trader works on the floor of the New York Stock Exchange (NYSE) in New York, U.S., on Monday, Oct. 31, 2016. U.S. stocks rose from a six-week low amid an increase in deal activity as traders assessed the outlook for the presidential election and interest rates in the world's largest economy. Photographer: Michael Nagle/Bloomberg via Getty Images

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The NYSE American trading delay is the second to be proposed since IEX won approval. The Chicago Stock Exchange in August outlined plans to adopt what it calls a Liquidity Taking Access Delay, a 350-microsecond delay for those who trade against resting orders on the exchange.

It also follows NYSE unusual decision to take aim at some of its biggest clients over their need for speed. In a letter to the Securities and Exchange Commission responding to criticism from the likes of Citadel, Wolverine Trading and trade body SIFMA, NYSE said some of those firms "have chosen to build business models based on speed."

Here's the NYSE statement:

NYSE Group (NYSE), part of Intercontinental Exchange (NYSE:ICE), today detailed its equity markets strategy, which aims to deliver greater choice for corporate and ETF issuers and to investors by offering four unique exchange venues, including an exchange designed exclusively for small and mid-cap companies.

The group's iconic New York Stock Exchange will continue to operate as the premium venue for corporate listings, and the only market to offer floor-based Designated Market Makers (DMMs) delivering the leading market quality and flawless IPOs. The floor brokers on the NYSE continue to act in an agency-only capacity, offering unique insight and access to the Parity allocation, which increases fairness and reduces dependence on speed, and the NYSE's liquid closing auction. NYSE previously announced its plan to expand NYSE's exclusive floor-based trading model to include all listed securities in the second half of 2017.

With its heritage as the American Stock Exchange, NYSE MKT, the market for small to mid-cap companies, will be known as NYSE American, following regulatory approval. NYSE American will be a first-of-its-kind exchange that brings the strengths of NYSE's features, such as electronic DMMs with quoting obligations assigned to each NYSE American listed company. NYSE American will also file rules with the SEC for new features that promote midpoint trading, including a 350 microsecond delay upon order entry, proprietary data and outbound routing, as well as a Discretionary Pegged Order.

Said Tom Farley, NYSE President: "As U.S equity markets have become increasingly complex due to fragmentation and dark pools, we are committed to providing listed companies, investors and market participants with more choice on how they list and trade with us in a way that best meets their needs. As we enter our 225th year as the global leader in trading and listings, we are continually evolving our markets to serve our customers in a very dynamic marketplace."

Farley continued, "As we move through 2017 and begin offering these enhancements, NYSE Group will ultimately operate four distinct exchanges for issuers and investors, each with its own market model. We recognize certain market models are appropriate for ETFs or less liquid securities, and we are excited to provide our customers with more choice in how they list, invest and trade."

NYSE American will provide a unique, efficient market combining the benefits of electronic DMMs and mid-point trading strategies.